The present invention relates generally to a vacuum coater device and, in particular, to a mechanism for supporting and manipulating the workpieces within the coating chamber of such vacuum coater device.
It will be appreciated that many parts in a gas turbine engine, including those in the high pressure turbine, combustor, and augmentor, are subjected to high temperatures. In order to enable such components to withstand such environment, it has been found desirable to apply a thermal barrier coating thereto (e.g., a durable physical vapor deposition (PVD) thermal barrier coating (TBC)). This is typically accomplished by means of a specialized device known as a vacuum coating apparatus, where the parts are subject to various process steps during the application cycle. Such process steps generally include loading the workpieces into the vacuum coating apparatus, heating the workpieces to a predetermined temperature, coating the workpieces in a desired manner, and unloading the workpieces from the vacuum coating apparatus.
The prior art discloses vacuum coaters which have performed the described process steps in essentially a linear fashion, where the workpieces are transported directly from one station to the next. One particular configuration is disclosed in U.S. Pat. Nos. 6,946,034 and 6,863,937 to Bruce et al., which is owned by the assignee of the present invention and is hereby incorporated by reference. These patents disclose a physical vapor deposition apparatus having a symmetrical arrangement with a preheat chamber and a loading chamber located on each side of a coating chamber. In this design, a rake unit loaded with parts to be coated may enter from either side of the coating chamber. This arrangement is inherently more efficient that an apparatus having a single linear load capability. Besides allowing a second rake unit to be heated in the preheat chamber while a first rake unit is undergoing the process in the coating chamber, additional rake units may be loaded with parts in the adjacent loading chamber.
One important aspect of coating the workpieces in a vacuum coating apparatus involves the ability to provide the proper coating distribution, particularly when such workpiece has a complex configuration. In order to do so, it has been found that the workpieces are preferably rotated and/or oscillated so as to achieve deposition of the coating material on all surfaces in a desired manner. U.S. Pat. No. 6,056,828 to Rick et al. and U.S. Pat. No. 5,985,036 to Anderle disclose exemplary devices for rotating and shifting movement of a substrate.
It has been found, however, that the mechanisms for supporting and manipulating the workpieces within the coating chamber of a vacuum coating apparatus are inherently complex and costly. This stems primarily from the remote location of the drive systems from the workpiece holders, thereby requiring a network of shafts and bevel gears to traverse the distance therebetween. Further, a dual shafted system is typically utilized to protect the mechanism against the harsh environment of the coating chamber.
Accordingly, it would be desirable for a vacuum coating apparatus to be developed which improves the support and manipulation of workpieces within the coating chamber. Besides producing the desired coating distribution, it would also be desirable for such configuration to be less complex and less costly than the current oscillating system. Of course, it would be also expected that such a mechanism work efficiently with the requirements of the electron beam guns therein.